1. Field of the Invention
The present invention relates to a digital communication technique and in particular to concepts for a message communication via channels having a strong fading, like e.g. radio channels.
2. Description of the Related Art
WO 00/367,783 discloses a device and a method for transmitting information and a device and a method for receiving information. The device for transmitting information includes an information source, a redundancy-adding encoder having a code rate smaller than ½, a separator for separating the output of the encoder into two separated data streams, wherein a data stream is transmitted via a first channel, while the other data stream is transmitted via a second channel. The redundancy-adding encoder enables a forward error correction which is employed in a receiver-sided decoder in order to guarantee a good receiving quality.
The first and the second channel are different by the fact that they are spatially different and that in addition a time diversity function is integrated, i.e. in so far that an information transmitted via the first channel is again transmitted via the other channel at a later point of time.
On the receiver side two receivers exist, which are different from each other, for receiving the signal transmitted via the first channel on the one hand and receiving the signal transmitted via the other channel on the other hand. The receiver output signals are combined using a combiner and fed to a decoder, which is for example set up as a Viterbi decoder and whose output values are fed into a Reed-Solomon decoder.
In this known transmitting/receiving system, which may be employed using two satellites arranged at different positions as a transmitter, the satellites are implemented such that they transmit in different frequency bands. This way it is easily possible to differentiate the signal of the one satellite from the signal of the other satellite, as the satellite receiving signals lie in different frequency bands and may be received in a frequency-selective way.
Disadvantageous about this concept is the fact, however, that two complete frequency bands are required, i.e. a first frequency band on which the first satellite is transmitting and a second frequency band on which the second satellite is transmitting.
In general, however, the bandwidth of one transmission channel is a scarce commodity, so that frequently only very little bandwidth is available for an application or that the bandwidth required by one application has to be paid for expensively. This substantially increases the costs for a system. In particular with broadcasting applications in which the development and installation effort of the transmitters and the satellites has to be divided among the receiving devices, this leads to a rise in costs of the receiving devices. In particular on the competitive market of broadcasting receivers, however, already little or mean price differences may cause that one system is accepted on the market, while another system does not prevail and disappears from the market.